An ultrasonic transducer includes an array of piezoelectric posts, emitting electrodes, and receiving electrodes. Each of the piezoelectric posts corresponds to an emitting electrode and a receiving electrode. When in operation, a voltage is applied to the piezoelectric posts via the emitting electrodes and the receiving electrodes, the piezoelectric posts emit ultrasonic wave to an object, and the piezoelectric posts receive the ultrasonic wave reflected by the object, the contour of the object, i.e., the fingerprint of a finger, applied to the ultrasonic transducer can be detected. However, because of the material and process of the ultrasonic transducer, the thicknesses of the emitting electrodes corresponding to different piezoelectric posts may be different, and the thicknesses of the receiving electrodes corresponding to different piezoelectric posts may be different, which results in the emitted ultrasonic wave being uneven, and the received ultrasonic wave being uneven. Thus, the detection accuracy of the ultrasonic transducer is decreased.